tossOriginal articlePainting the Wheels of a Moving Train: (opens in new tab)
Toss Design System (TDS) underwent its first major color system overhaul in seven years to address deep-seated issues with perceptual inconsistency and fragmented cross-platform management. By transitioning to a perceptually uniform color space and an automated token pipeline, the team established a scalable infrastructure capable of supporting the brand's rapid expansion into global markets and diverse digital environments. ### Legacy Issues in Color Consistency * **Uneven luminosity across hues:** Colors sharing the same numerical value (e.g., Grey 100 and Blue 100) exhibited different perceptual brightness levels, leading to "patchy" layouts when used together. * **Discrepancies between Light and Dark modes:** Specific colors, such as Teal 50, appeared significantly more vibrant in dark mode than in light mode, forcing designers to manually customize colors for different themes. * **Accessibility hurdles:** Low-contrast colors often became invisible on low-resolution devices or virtual environments, failing to meet consistent accessibility standards. ### Technical Debt and Scaling Barriers * **Interconnected palettes:** Because the color scales were interdependent, modifying a single color required re-evaluating the entire palette across all hues and both light/dark modes. * **Fragmentation of truth:** Web, native apps, and design editors managed tokens independently, leading to "token drift" where certain colors existed on some platforms but not others. * **Business expansion pressure:** As Toss moved toward becoming a "super-app" and entering global markets, the manual process of maintaining design consistency became a bottleneck for development speed. ### Implementing Perceptually Uniform Color Spaces * **Adopting OKLCH:** Toss shifted from traditional HSL models to OKLCH to ensure that colors with the same lightness values are perceived as equally bright by the human eye. * **Automated color logic:** The team developed an automation logic that extracts accessible color combinations (backgrounds, text, and assets) for any input color, allowing third-party mini-apps to maintain brand identity without sacrificing accessibility. * **Chroma Clamping:** To ensure compatibility with standard RGB displays, the system utilizes chroma clamping to maintain intended hue and lightness even when hardware limitations arise. ### Refined Visual Correction and Contrast * **Solving the "Dark Yellow Problem":** Since mathematically consistent yellow often appears muddy or loses its "yellowness" at higher contrast levels, the team applied manual visual corrections to preserve the color's psychological impact. * **APCA-based Dark Mode optimization:** Utilizing the Advanced Perceptual Contrast Algorithm (APCA), the team increased contrast ratios in dark mode to compensate for human optical illusions and improve legibility at low screen brightness. ### Designer-Led Automation Pipeline * **Single Source of Truth:** By integrating Token Studio (Figma plugin) with GitHub, the team created a unified repository where design changes are synchronized across all platforms simultaneously. * **Automated deployment:** Designers can now commit changes and generate pull requests directly; pre-processing scripts then transform these tokens into platform-specific code for web, iOS, and Android without requiring manual developer intervention. The transition to a token-based, automated color system demonstrates that investing in foundational design infrastructure is essential for long-term scalability. For organizations managing complex, multi-platform products, adopting perceptually uniform color spaces like OKLCH can significantly reduce design debt and improve the efficiency of cross-functional teams.
